This application, Feelings and Body Investigators (FBI): Interoceptive Exposure for Child Abdominal Pain is in response to PA-11-177, Translational Research for the Development of Novel Interventions for Mental Disorders (R21/R33). We propose development and pilot-testing of an acceptance- based behavioral treatment for young children (5-8 years old) with functional abdominal pain (FAP; R21, n=26, R33, n=100). FAP is one of the most frequent somatic syndromes in young children, causes significant impairment, and is predictive of psychiatric and pain disorders later in childhood and in adulthood. No treatments exist for very young children with FAP. Research supports that FAP is influenced by: (1) early pain on the neurodevelopment of the gut-brain axis and (2) maladaptive interactions with the social environment that inadvertently increase somatic fear. These vulnerabilities provide targets for early intervention. OBJECTIVE: To develop and pilot an intervention for FAP based on fundamental neuroscience research on the aberrant neurodevelopment of the gut-brain axis and subsequent modification by the social environment. Our treatment 1) links intervention strategies to unique patterns of neural circuit maturation associated with early visceral pain on the gut-brain axis, 2) adapts acceptance-based behavioral strategies used to address psychopathology in older children to younger children, and 3) incorporates caregivers as role models and facilitators based on attachment research. METHODS: Our ten session intervention trains children to be Feeling and Body Investigators. Half of the sessions will be done in clinic and half at home via web-camera to facilitate generalization. During the treatment child/caregiver dyads will 1) gather body clues (Learn), 2) investigate (Experience: perform interoceptive mystery missions to explore a body sensation), 3) organize body clues (Contextualize: recall other contexts that evoke similar sensations), and 4) go on increasingly daring missions (Challenge: decrease avoidance and safety behaviors). In the R21 phase we will develop and refine the FBI intervention in 26 child- caregiver dyads. In the R33 phase we will randomize 100 children with FAP to FBI or an active control (parent education with standard medical care) to conduct a pilot-test of the feasibility, acceptability, an clinical significance of FBI compared with an active control treatment. We will use epidemiological methods to screen all eligible children attending primary care practices so that our sample will be representative of young children with FAP, not simply a convenience sample. If we are successful, young children with FAP who complete our FBI early intervention will learn to experience changes in the viscera as fun and fascinating, rather than scary, and will develop new capacities for pain management, adaptive functioning, and emotion regulation. The success of our early intervention for FAP in young children will also have broad implications for the treatment and prevention of mental illness and chronic abdominal pain.